The document 3GPP TS 23.141 V0.0.0. “3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Presence Service; Architecture and Functional Description (Release 6)” dated June 2002 discloses a service which is referred to as a “presence service” in which a presence computer (presence server) monitors characteristics of selected communications subscribers. Such characteristics include, for example, the respective current accessibility by telephone, by the short message service (SMS) or by e-mail. Information about such characteristics is gathered and is transmitted in the form of presence data to communications terminals which require such presence data. Chapters 4 and 5, in particular, describe how such information can be provided by the selected communications subscribers, by technical facilities (for example switching centres, home location registers) in a mobile radio network, or by technical facilities (for example calendar applications of a service provider) arranged outside the mobile radio network.